The present invention relates to a process for removing a scale containing calcium oxalate adhered on an inner wall of an apparatus.
Scales adhered on an inner wall of an apparatus used in various processes are made of calcium oxalate as a main component.
These scales have not easily dissolved by the conventional methods, since the scale containing calcium oxalate as a main component (hereinafter referred to as a scale of calcium oxalate) is not easily dissolved in a strong acid or a strong base.
Such scales are mainly formed on an inner wall of an evaporator for concentrating a waste solution discharged from a digester (black liquor) in a sulfite pulp process, a chemiground pulp process or a semichemical pulp process. Such scales are also formed on an inner wall of an apparatus for producing a cane sugar or a beet sugar. Such scales are further formed on an inner wall of an apparatus for producing beer, whisky or wine. Such scales are also formed on an inner wall of a bleaching tower for bleaching a pulp.